Ytdyklly

I just was reading the Lost Mine of Phandelver adventure when I noticed that page 21, section "3. Trapped Hall" says:

Awarding Experience Points

Divide 100 XP equally among the characters if the party avoids or survives the pit trap.

Does that mean that in normal encounters/dungeons/whatever characters earn XP for avoiding or surviving traps? My DM never rewarded me with XP for that stuff!

In the case it's yes, how much XP is awarded? As far as I know, neither the DMG nor XGtE (which has guidelines about traps) explain how to calculate the XP of a trap.

Additionally, I found this answer to "How should I award XP for traps?" on RPG.SE - but if that answer says you shouldn't do this, why does the Lost Mine of Phandelver adventure (which, as far as I know, is an official campaign) do it?

XP is entirely up to the GM

In 5e, the GM can award XP for anything they choose. XP represents experience, and disarming or avoiding a trap is an experience. You don't need guidance on this in RAW, but you could treat it as having the xp value of a monster of a CR equivalent to the PC's average levels, plus or minus 10% depending on how deadly you estimate it to be, if you really need a mechanic.

Personally, I find tracking XP per monster, per encounter, etc extremely fiddly and not worth the effort, and I go for a lump-sum XP award per session, with bonuses for good RP, cool tactics, progress, teamwork, etc. Or use the milestone progression technique and forego XP altogether. Since it's no longer used as a fuel for crafting magic items, like in prior editions, it's not super important as long as your level progression is a reasonable pace.

Xanathar's Guide to Everything offers optional XP-for-traps

From page 113 to 121 on XGtE, traps are compared to monster CR as compared to tiers of play (1-4 5-10, etc). On page 118 there is a recommended XP award for complex traps: 650 XP for Tier 1, 3850 for Tier 2, 11,100 for Tier 3, and 21,500 for Tier 4. Needless to say, some of these example complex traps are fiendish. You can use that general guideline, scaled down a bit, for your own traps.

If you don't have Xanathar's Guide, there was a UA article in 2017 with similar suggestions for trap complexity(much of it ended up in XGtE). You need to estimate how difficult or deadly a trap is for a party of level X, compared to the deadliness of a CR Y monster to get an estimated XP award.

Even with the broad guidelines given, tinkering a bit with it and customizing it for your table is part of the DM's art.

FWIW, I discovered rather by accident that waaaaay back when, when Thieves were being played early on in the Twin Cities and Lake Geneva area, that thieves usually got their level X 100 XP for defeating traps .... but as that was a different edition and philosophy (1 GP = 1 XP in that system) it may not suit your needs in this edition. (I'll try to find the link, it's elusive at the moment). The idea of XP for traps is pretty old.

Well, I certainly did hand out XPs in my campaign for spell use, also
successful tracking by rangers, use of thief abilities by any PC so
doing, that sort of thing. ~Gary Gygax on enworld boards